Cosmic flows in the nearby universe from Type Ia Supernovae

Abstract

Peculiar velocities are one of the only probes of very large-scale mass density fluctuations in the nearby Universe. We present new "minimal variance" bulk flow measurements based upon the "First Amendment" compilation of 245 Type Ia supernovae (SNe) peculiar velocities and find a bulk flow of 249 +/- 76 km/s in the direction l= 319 +/- 18 deg, b = 7 +/- 14 deg. The SNe bulk flow is consistent with the expectations of ΛCDM. However, it is also marginally consistent with the bulk flow of a larger compilation of non-SNe peculiar velocities (Watkins, Feldman, & Hudson 2009). By comparing the SNe peculiar velocities to predictions of the IRAS Point Source Catalog Redshift survey (PSCz) galaxy density field, we find Ω_{m}^{0.55} σ_{8,lin} = 0.40 +/- 0.07, which is in agreement with ΛCDM. However, we also show that the PSCz density field fails to account for 150 +/- 43 km/s of the SNe bulk motion.